Balancing the airflow through a duct system or furnace is a necessary step in effectively heating or cooling a modem home. Many designs accomplish this using an adjustable damper device which requires some method of ensuring that the damper does not move once it is adjusted. This may involve tightening a nut or using a screw.
One such system is described in U.S. Pat. No. 5,806,830 which issued on Sep. 15, 1998. That patent describes a plastic collar for joining ventilation ducts in a forced air system. An adjustable damper is disclosed and is controlled by a conventional wing nut and lever arrangement, positioned on the exterior surface of the duct so as to be adjusted manually. The lever is attached directly to a damper valve inside the collar in the air flow. Adjustment is made by loosening the wing nut by hand, maneuvering the lever arrangement into the desired position, and finally tightening the wing nut by hand.
This device has proved to be popular but, however there are disadvantages. The mechanism is not self-locking and can therefore easily be positioned incorrectly or accidentally. The adjusting mechanism is also placed on the exterior surface of the collar exposing it to the outside environment. This causes three problems. Firstly it increases the chance of the mechanism being damaged or accidentally repositioned. Secondly it allows for the air within the ventilation system to leak out into the outside environment making the ventilation system less efficient. Finally, this system does not allow for an effective vapor barrier to be made around the collar body.
Another such system is described in U.S. Pat. No. 4,628,954 which issued on Dec. 16, 1986. That patent describes a damper to be positioned in an air outlet. The damper valve has a butterfly shape and does not rotate to vary airflow but opens and closes from a middle pivot. The damper valve is adjusted manually by insertion of a tool into the damper mechanism where torque is provided to a worm gear which controls the position of the damper valve. The damper is for use only in an air outlet and does not include catch teeth or a spring biassing arrangement.
In addition, none of the prior art utilizes a damper valve with flexible or rigid insulated pipe.
The present invention uses a mechanism whereby the damper valve is held in position by spring tension which force gear teeth on the damper rod into mating gear teeth in the inner collar body thus making the damper self-locking. Adjustment is carried out by inserting a screwdriver through a sealable aperture and into a receptacle and then pushing inwardly, against the spring biassing arrangement, thereby releasing the mating teeth and therefore releasing the damper rod and inner collar body. Once the gear teeth are released turning the screwdriver, and with it the damper rod and damper valve, will adjust the airflow. Once the pressure is released, the damper will lock by mating with the gear teeth on the inner collar body. The screwdriver can then be removed and the aperture resealed.